See, your old man was a tier 1 I'd bet, and seeing he's probably bound to a rule of 70, which he more than qualified for. 65 + 43 = 108, so he gets a ton of credit for going over his retirement age. According to their calculations:
The newer generation jumps to highest 5 years of salaries, which is another turn-off for new teachers. Also, big difference is the normal retirement age. In earlier tiers, you can retire once you satisfy the rule of 80, but in Tier 5 you have to be at least 62 to qualify for normal retirement age, regardless if you've met rule of 80. So consider your dad here, he would be eligible to retire under normal circumstances at age 51 with roughly 67% of his highest three years, while if he were to started today, he'd need an additional 11 years of service (but would get a bump in his total percentage after the additional 11 years, bringing his total to 92% of his pay).
The other irritating thing: legislature will tweak the newer tiers in ERS and TRS, changing the retirement requirements every few years until a new tier is released, and usually those tweaks mean less money in retirement, additional years of service, etc. Big reason I yanked my state pension after the better part of a decade working for the state.